The present invention relates generally to loss of voltage detectors, and in particular to circuitry for detecting and indicating the loss of voltage in a power distribution system.
It is often necessary in commercial electrical distribution systems to provide an alarm and/or control function in the event of a power interruption. For example, it may be required that electrical power generating equipment be started in the event of a power failure to maintain critical equipment in operation, or that certain types of electrical equipment be disconnected from power mains in the event of a power failure to prevent damage upon restoration of power. Furthermore, in the case of multi-phase power systems, it may be required that certain equipment be disconnected following a failure in one phase in order to avoid potentially damaging single-phase operation of the equipment. Loss of voltage detectors, particularly those adapted for use with commercial power distribution systems, are useful for automatically implementing such procedures in the event of power failure.
In the case of high voltage power mains, high impedance coupling of the loss of voltage detector to the power mains is desirable in order to provide isolation from the high voltages present in the mains. The loss of voltage detector of the present invention utilizes such preferred high impedance coupling for both energization of its circuitry and for providing an external control effect. Consequently, coupling to high voltage conductors can be readily accomplished at such conventional locations as high impedance underground cable termination test points.
The loss of voltage detector of the present invention constitutes an improvement over the detector described in U.S. Pat. No. 4,550,288 of the present inventor, in that it provides a higher impedance input, facilitating its use high impedance test points and on high voltage overhead lines, and a faster recharge time, facilitating the detection of recurring voltage interruptions. Like the detector described in U.S. Pat. No. 4,550,288, the detector of the present invention provides a control effect in the form of closure of a set of relay contacts, which can easily be adapted to actuate other electrical systems and equipment, as described in the patent.
Accordingly, it is a general object of the present invention to provide a new and improved loss of voltage detector.
It is another object of this invention to provide a loss of voltage detector having a high impedance input suitable for use in conjunction with high impedance test points and high voltage electrical power lines.
It is another object of this invention to provide a new and improved loss of voltage voltage detector which is energized and triggered by means of high impedance coupling to a high voltage power line.